<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>12-正方形-正圆</title>
		<style type="text/css">
			.box{
				width:200px;
				height:200px;
				border-radius:50%;
				background:red;
			}
		</style>
	</head>
	<body>
		<div class="box"></div>
	</body>
</html>
